Colom had nearly 53 percent of the vote, while Perez, of the conservative Patriotic Party, had 47, according to results published on Guatemala's Electoral Tribunal Web site.

Perez acknowledged that Colom's lead was insurmountable.

"We are going to be a constructive opposition," said Perez, who ran on a tough anti-crime platform.

"We're willing to keep fighting the war against impunity, the war against corruption and against violence."

Colom, a 56-year-old former vice economy secretary and ordained Mayan minister, promised jobs, a judicial overhaul and increased social spending in Guatemala, where more than half of the country's 13 million people live on less than $2 a day.

He said he would use his experience brokering a civil war peace pact to reduce crime.

"If you don't know the root of the problem, it is hard to solve it," Colom told reporters on the eve of the vote. "And we have been studying the causes behind our soaring crime rate for six years."

Calm prevailed during the vote, which was guarded by more than 30,000 police and soldiers, on alert after weeks of campaigning marred by violence. There were no reports of serious incidents Sunday, when about 47 percent of the 6 million registered voters went to the polls.

Security was a top issue among voters in Central America's most violent country, with more than 5,000 homicides per year.

Perez, also 56, held a slight lead in polls heading into the vote. He promised to institute the death penalty, hire more police and send soldiers into the streets to fight crime.

A former military intelligence director, he has been accused of overseeing massacres during Guatemala's 1960-96 civil war, which he denies.

Ruben Cruz, 60, a studio photographer, said Guatemala must deal with gangs that extort money from businesses and residents. He said thugs come to his home every four months to collect what they call taxes.

"I voted for Colom because he offers jobs for a lot of people, but also to fight criminals," Cruz said.

Political violence made for a harrowing campaign, with more than 50 candidates, party activists and their family members killed. Last month, Perez's secretary and a presidential security guard were gunned down.

In the first round of voting in September, Perez and Colom finished far ahead of 12 other candidates, including Nobel winner and Mayan activist Rigoberta Menchu. Pre-election polls gave Perez a slight edge in Sunday's vote.